Runnable or Thread - Deciding the Better Choice in Java

In this short article, we will explore which is a better choice when creating a multithreaded environment - implementing the Runnable interface or extending the Thread class.

Java provides two options when creating a multithreaded environment:

1. implementing the Runnable interface
2. extending the Thread class. 

Both accomplish the same task of executing code in a separate thread, but deciding which one to use requires a deeper understanding. Let's unravel these two options, outlining their differences and determining which one serves better in specific situations.

Overview of Thread and Runnable

Thread Class 

The Thread class encapsulates a thread of execution in Java, making multithreaded programming straightforward. To create a new thread, you can extend the Thread class and override its run() method:

public class ThreadExample extends Thread {

    // run() method contains the code that is executed by the thread.
    @Override
    public void run() {
        System.out.println("Inside : " + Thread.currentThread().getName());
    }

    public static void main(String[] args) {
        System.out.println("Inside : " + Thread.currentThread().getName());

        System.out.println("Creating thread...");
        Thread thread = new ThreadExample();

        System.out.println("Starting thread...");
        thread.start();
    }
}

Output:

Inside : mainCreating thread...
Starting thread...Inside : Thread-0

Runnable Interface 

The Runnable interface represents a task that can be executed concurrently by multiple threads. It has a single method, run(), that is intended to contain the code executed in the thread:

public class RunnableExample implements Runnable {

    @Override
    public void run() {
        System.out.println("Inside : " + Thread.currentThread().getName());
    }
    
    public static void main(String[] args) {
        System.out.println("Inside : " + Thread.currentThread().getName());

        System.out.println("Creating Runnable...");
        Runnable runnable = new RunnableExample();

        System.out.println("Creating Thread...");
        Thread thread = new Thread(runnable);

        System.out.println("Starting Thread...");
        thread.start();
    }
}

Output:

Inside : main
Creating Runnable...
Creating Thread...
Starting Thread...
Inside : Thread-0

Runnable vs. Thread: The Comparison 

Extensibility

Java is a single inheritance language, meaning a class can only inherit from one superclass. If you extend the Thread class, your class can't extend to any other class. However, a class can implement multiple interfaces. Therefore, Runnable offers more flexibility when it comes to extending other classes in your threading class. 

Encapsulation 

The Runnable interface represents a task, which can be sent to any thread for execution. It separates the task to be executed (in the Runnable's run() method) from the actual thread controlling the execution (Thread class). This separation follows the principle of encapsulation, making the code more modular and manageable. 

Object Sharing 

When several threads share the same instance of a Runnable object, they share the same object and thus the same state. In contrast, threads don't share their state when they're created using different Thread objects.

The Better Choice? 

Given these considerations, implementing the Runnable interface generally comes off as more flexible and modular. Runnable allows you to inherit from other classes and promotes object-oriented practices like inheritance, encapsulation, and object sharing, which can be useful for managing states across multiple threads. 

However, extending the Thread class can be more straightforward for simple use cases, and it does provide additional methods for thread control. 

To sum it up, Runnable should be the first consideration for most multithreading tasks due to its advantages, but understanding the Thread class is essential to grasp the overall picture of Java's multithreading environment. 

Remember that the right choice always depends on the specific requirements of your program. So, evaluate these options carefully, understand the benefits and drawbacks, and make the most informed decision based on your application's needs.